The first Space Shuttle didn't reach orbit until 1981, but NASA was working on designs for nearly a dozen years before that. And looking at the progression of these concept drawings, you can see how compromises were made and budgets were cut. Here's the evolution of the Space Shuttle, in pictures.

NASA's Spacecraft Design Division (SDD) began serious work on developing concepts for the Space Shuttle in early 1970. The drawings below illustrate most of the configurations that were considered, in more or less chronological order. (The first number accompanying each design is the series number, followed by the date of the design.) What's astonishing is the rapidity with which design changes were made, with many being made weekly.

I've sometimes thought that this series could be animated, so one could watch the shuttle become both more compromised and more complex as it evolved and budgets were cut. What's kind of sad is seeing what a totally cool spaceship the shuttle might have been.

One of the first major design changes was from straight-wing (originally proposed by Mercury spacecraft designer Max Faget) to delta-wing. This occurred with Orbiter 022B in May 1971. The other major change that affected the final design of the shuttle was the decision to abandon a piloted, reusable, fly-back booster—which had been an integral part of Space Shuttle design from the beginning—in favor of expendable external tanks and reusable strap-on boosters. This occurred with Orbiter 026, also in May 1971. After this, SDD engineers focused on parallel-burn approaches, in which the shuttle's main engines are firing at the same time as the booster's. These designs most often took the form of sequential, staging or stage-and-a-half designs.

Shuttle 040C inaugurated the now-familiar external fuel tank flanked by a pair of solid-fuel boosters. The only significant differences between 040C and the shuttle design that was eventually flown were that the solid-fuel boosters were attached to points close to the shuttle—between the external tank and the shuttle's wings—and that the external tank was outfitted with large wings. In March 1973, NASA committed to the parallel-burn configuration.

Although several shuttle concepts were considered following model 040C, that was the configuration that was eventually handed over to Lockheed, McDonnell-Douglas, Grumman and North American Rockwell for final development. In March, 1972, Authority to Proceed (ATP) was granted and the shuttle quickly progressed through the Program Readiness Review (PRR) stages to its final configuration.